1. Field of the Invention
The present invention relates to a small portable terminal and, more specifically, to a portable terminal having many functions where amount of information input/output varies in accordance with the functions.
2. Description of the Background Art
Recently, a small portable terminal, represented by a portable telephone, that can be held by one hand comes to incorporate various functions. For example, it incorporates functions of a portable terminal such as a telephone and a personal computer, mainly including communication functions represented by telephone (conversation) function, as well as creation, transmission and display of electronic mails. Along with the increasing number of functions, many proposals on device structures have been made that allow operations in different forms suitable for the states of use of the portable terminal.
US2004/189597A1 discloses foldable and slidable type portable telephones. When the portable telephone is put in a bag or a pocket, an upper case is folded or slid to close and hide an operating panel on the lower case, in order to prevent unintentional button operation. At the same time, in order to allow simple operation such as checking an incoming mail while the portable telephone is closed, an opening (for a folding type) or a U-shaped cutout (for a sliding type) is formed on the upper case, so that the user can manipulate a pointing device provided on a surface of the lower case through the opening or the cutout.
US2005/052837A1 discloses a portable terminal having two wedge-shaped bodies slidably coupled to each other to provide space margin mainly for positioning a camera mechanism. The wedge-shaped bodies are normally combined to form a rectangular box, allowing compact storage. At the time of use, the bodies are slid with respect to each other, so that the overall body comes to have a prescribed length convenient for use. As the body is wedge-shaped, the portion corresponding to the bottom of the wedge is thick enough to accommodate camera or other mechanism with ample room.
Japanese Patent Laying-Open 2006-19925 (FIGS. 16, 47 to 49, 55 and 56) discloses a portable terminal having a function mainly allowing viewing of television (hereinafter denoted as “TV”) broadcast (typically, 1-segment broadcasting service in Japan for distributing TV broadcast to portable terminals.). The portable terminal includes a first case having an operation panel and a second case having a display, and by rotational sliding, it is possible to switch between a state in which the operation panel of the first case is covered with the second case, and a state in which the operation panel of the first case is exposed and the display of the second case is set in lateral (landscape) arrangement. Particularly, a mechanism is adopted that allows easy, one-hand operation for rotationally sliding the second case.
As the 1-segment broadcasting service has started, the function allowing viewing of TV broadcast would be an important requirement for future portable terminals. For satisfactory viewing of TV broadcast, a display screen is preferred to be as large as possible and landscape display capability is desired. Further, for the purpose of playing games on portable terminal displays, which are now popular, a display screen as large as possible and allowing both landscape and portrait arrangements is desired.
At the same time, in order to realize other functions of the portable terminal, it is also necessary to provide relatively large number of buttons and the like, such as numeric buttons and cursor keys. Particularly, when an application requiring relatively frequent text input, such as electronic mailing, is to be implemented, a considerably large number of buttons must be provided. Most of such buttons, however, are unnecessary when one views TV broadcast or plays a game and, these buttons are rather troublesome as unintended touching may cause erroneous operation. Therefore, it is preferred that such buttons are hidden at the time of receiving TV broadcast or playing a game.
In the portable telephone disclosed in US2004/189597A1, when one views TV broadcast on a main display, the operation panel is exposed, no matter whether the telephone is the foldable type or slidable type. In such a state, the user is forced to view the TV broadcast while paying attention not to erroneously touch any of the buttons. As a result, the user may feel it a bother. The foldable type may allow the user to view TV on a sub-display provided on a rear surface, with the portable telephone kept folded; however, the sub-display might be too small to enjoy a TV program.
The portable terminal described in US2005/052837A1 has operating portions not directly related to TV viewing, such as a camera and camera operating buttons, arranged on a side surface, and the operating portions are always operable no matter whether the bodies are extended or not. In this case also, the user must pay attention not to erroneously press any button unrelated to TV viewing, and hence, carefree TV viewing is not expected.
The portable terminal described in Japanese Patent Laying-Open No. 2006-019925 realizes both portrait and landscape displays, and switching from the portrait to landscape display can be realized advantageously with one hand. The structure of the terminal, however, is such that all buttons and the like are hidden in the portrait display state, and all the buttons and the like are exposed in the landscape display state. As a result, when the user views TV with the portrait display of the device disclosed in Japanese Patent Laying-Open No. 2006-019925, quick key operation is impossible. When one views TV with the landscape display, on the contrary, all the buttons and the like are exposed, and hence, it would be difficult to enjoy TV broadcast, as care is demanded to avoid erroneously touching buttons and the like. In order to avoid such a problem, a special consideration is necessary. For example, a channel switch button is placed right beside the display portion.
Further, though the portable terminal described in Japanese Patent Laying-Open No. 2006-019925 allows switching between portrait display and landscape display with one hand, the direction of display is rotated by 90° before and after the switching in either direction. As the display is rotated when the posture is switched, it is necessary to change the manner of display in accordance with the posture and the manner of use after the posture is switched with one hand, and such an operation might be so troublesome as to cancel the advantage of easy posture switching with one hand.
Along with increasing functions of portable terminals such as portable telephones as described above, the amount of text to be input through the operating portion has been increasing. In any of the terminals according to US2004/189597A1, US2005/052837A1 and Japanese Patent Laying-Open No. 2006-019925, however, the number of buttons or keys arranged on the operating portion is limited. As a result, an input method must be adopted in which a plurality of characters are allocated to one button or one key and a desired character is input by pressing one key a number of times. Such an input method is problematic, as the input takes much time. A clear solution to this problem is to provide larger number of buttons or keys. However, increase in size of a portable terminal is limited, and the number of buttons is desired to be as small as possible to prevent exposure of unnecessary buttons when viewing TV. Under the circumstances, a solution has not been found. Thus, the user cannot use the portable terminal with optimal key configuration suitable for the state of use.